The present invention relates to a production apparatus and, more particularly, to a continuous production device for bodies having a reinforced stabilizable profile section.
Production device of the aforementioned type are disclosed in, for example, British application No. A-2088320 and French No. A-2312356 wherein a mandrel is rotatably driven around a longitudinal axis with a helically wound support being wound onto the mandrel. The profiled section bodies may, in particular, be inward curved bars made of reinforced stabilizable material.
Such bars can be used to shape rigid or flexible shafts, such as tubes, resistant to pressure differential, traction, compression, torsion or bending stresses.
The term "stabilizable material" means that the bodies can assume a stable form via a physical or chemical process, such as melting with cooling or cross linkage. These materials may, for example, be thermoplastic materials, thermosetting materials, elastomers or metals.
Some prior techniques for producing profiled bars by using a mandrel or hollow section are, for example, described in U.S. Pat. No. 3.966.388 and FR-A-2.312.356, or in the French patent application EN. 86/05.093 which concerns a support simultaneously moulding several bars.
However, industrial application of these prior techniques has shown that there is a lack of flexibility of the production device due to an irregularity of the forward movement of the mould support on the mandrel and increased adverse effect when the production rate and/or the length of the mandrel is increased.
The length of the mandrel depends in particular on the stabilization of the material constituting the bars. Generally, this length increases relatively as much as the rotation speed of the mandrel, itself an increasing function of the production rate.
The use of long stabilization ovens authorizes the use of slow stabilization material, such as not very reactive resins, and thus allows for many advantages to be gained from this material, such as pre-reticulation.
This irregularity of forward movement is accompanied by blockages of the support and/or the section when the support is wound onto the mandrel, or when it moves forward, or even when it is evacuated.
These blockages can lead to deformations of sections and, more particularly, in curved bars which produce disastrous stresses when used, especially when finally installed, for the production of tubes.
In accordance with advantageous features of the present invention, a device for continuously producing reinforced stabilizable profiled section bodies is provided which includes a mandrel and means for driving the mandrel and means for rotationally driving the mandrel around a longitudinal axis thereof, with the mandrel supporting at least one helically wound support thereon. Means are provided for causing the support to move in a forward direction longitudinally on the mandrel, such as a slope, and means wind around the mandrel and onto the support of the reinforcement elements impregnated with stabilizable material. A stabilization means is disposed on at least one part of a length of the mandrel, and means are provided to separate the reinforced material having undergone stabilization from the mandrel. The support is wound onto a first extremity of the mandrel and separated from the mandrel at a second extremity.
This device in particular is characterized in that the first extremity of the mandrel includes an elevated first zone, known as a calibration bearing surface, on which the support is wound, with the bearing surface being long enough to drive the support via a capstan, effect and being limited in length so as to not impede the forward movement of the support on the mandrel.
Thus, by means of this calibration bearing surface, which may have a constant diameter, the longitudinal frictions of the support, on the part comprising a diameter restriction and called standard length of the mandrel, are considerably reduced. Because of this, the length of the mandrel may be quite large without risking blockages and overlaps of the support occurring on the mandrel, especially as regards its standard length. Similarly, the circumferential drive of the section via the capstan effect is much better controlled and the longitudinal drive, produced by the insertion of the support between the ramp of the mandrel and the final thread of the introduced support, is much more stable.
The second extremity of the mandrel could include a second elevated zone, known as an extraction bearing surface, on which the support is wound and from which the support unwinds. This extraction bearing surface has a suitable length and diameter adapted to allow for proper forward movement of the support on the mandrel when a disengaging traction is exerted on the support at the mandrel extremity.
The extraction boaring surface enables the extraction speed to be adjusted by roughly making it equal the feed speed. This arrangement prevents the accumulation of bars wich produces bars loops in the oven or prevents tractions on these bars, namely, detrimental residual stresses or malformation of bars during the use of bars and also blockages when forward driving of the support on the mandrel.
The extraction bearing surface is especially useful when the bars once extracted are routed to an automatic station, such as an automatic winding station.
The mandrel could comprise, at least on one part of the calibration bearing surface and possibly extraction bearing surface, an antiadhesive material adapted to prevent adherence because of possible projections of the stabilized material from the support onto the mandrel.
This invention also proposes the use of a system for lubricating a mandrel for profiled body production, in particular a mandrel as the one offered by the invention, which notably increases the flexibity of the use of devices employing such mandrels.
The device could comprise a suitable lubrication system to favor a longitudinal displacement of the support on the mandrel in the direction of the second extremity. This system could include a suitable lubricating fluid, at least as regards the contact between the support and the mandrel. This system could also include, at least on one part of the calibration and possibly extraction bearing surfaces, a material favoring sliding of the support on the mandrel. This material could be TEFLON, which is a registered trademark of Du Pont de Nemours.
Similarly, this invention proposes, especially for calibration and possibly extraction bearing mandrels as previously described, that at least one part of the extraction and/or calibration surface includes a coating suitable for selectively favoring circumferential friction, preferably without too adversely affecting the longitudinal friction of the support on the mandrel. In this way, the support shall be correctly rotationally driven and could move on large lengths without encountering the previously mentioned drawbacks.
When the profiled section bodies are inwardly curved profiled section bars, the support can comprise at least one groove forming a mould with a section roughly corresponding that of the bar to be obtained.
This invention also offers a process to continuously produce inwardly curved bars with a profiled section by a device comprising a combination of a mandrel, means driving this mandrel in rotation around its longitudinal axis, with the mandrel supporting at least one hollow section wound helically onto the mandrel, and the section comprising at least one groove forming a section corresponding to that of the section or profile to be obtained. Means wind around the mandrel and in the groove reinforcement elements impregnated with a stabilizable material, and reticulation means are disposed on at least one part of the length of the mandrel, with means separating the profiled reinforced material which has undergone stabilization from the mold.
In accordance with the process of the present invention, the hollow profile or section is wound onto a first extremity of the mandrel comprising a calibration surface by creating a capstan effect between the mandrel and the hollow profile and/or reinforcement element, and the hollow profile, lined with the reinforcement elements, moves longitudinally to a second extremity above one part of the mandrel having a diameter less than that of the calibration bearing surfaces, with the hollow profile then being separated from the mandrel at the second extremity.
In French patent application No. A-2049167, a production of fixed glass fiber bars embedded in thermosetting resin, with the bars having the shape of a helix, with the aid of a shaper cylinder as proposed wherein a profiled groove and a drive drum turning in the direction of the pitch of the helix are provided, with the drive drum driving the bars while they are hardening.